Triple-valve mechanism.



W. P. ATWOOD. TRIPLE VALVE MECHANISM.

APPLICATION FILED MAILZI. 1914. 1, 1 20,584 Patented Dec. 8, 1914.

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TRIPLE VALVE MECHANISM.

APPLICATION FILED mnxzx, 1914.

1,1 20,584. Patented Dec. 8, 19141 2 SHEETSSHEET 2.

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WALTER F. ATWOOD, OF AMARILLO, TEXAS.

TRIPLE-VALVE MECHANISM.

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Application filed March 21, 1914.

To all whom it may concern:

Be it known that I, WALTER F. A'rwooo, a citizen of the United States, residing at Amarillo, in the county of Potter and State of Texas, have invented certain new and useful. Improvements in Triple-Valve Mechanisms, of which the following is a specification.

This invention appertains to automatic fluid pressure brake systems and involves certain impr vements in what are commonly known as triple valves by which the application of air brakes is controlled.

One of the difliculties experienced in the operation of the triple valve as commonly used resides in the fact that oftentimes the main or triple slide valve does not move promptly to release position under the action of the triple piston connected therewith, owing to a slow rise in the train pipe pressure or the wearing of the packing rings of said triple piston resulting in a tendency for the train pipe pressure to equalize on opposite sides of said piston.

A further object of the invention has been to devise instrumentalities coacting with the triple valve mechanism in such a manner as to readily insure a proper operation of the valve means in the event of an overcharge of fluid. pressure, which gives rise to certain ditliculties in regard to the proper operation of the triple valve mechanism, as well known to those versed in this art.

In the carrying out of the invention 1 contemplate the provision of what may be broadly termed an auxiliary motor in the form of a fluid pressure actuated piston so arranged in respect to the triple piston of the main or triple slide valve as to forcibly act through intermediate parts on said triple piston to positively move the same mechanically to a release position in the event said triple piston and its slide valve do not assume such release position in response to the increase or rise in the train pipe pressure as controlled from the engineers valve.

The auxiliary motor above referred to is normally inactive and is controlled in its operation by special control mechanism which in turn is controlled in action by the train pipe pressure and the auxiliary reservoir pressure. as will be more fully pointed out in the following description and readily Specification of Letters Patent.

Patented Dec. 8, 1914.

Serial No. 826,295.

understood in connection with the accompanying drawings in Which:

Figure 1 is a sectional view showing a common type of triple valve with my improvements applied thereto, and the parts arranged in release position. Fig. 2 is a view similar to Fig. 1 showing the several cooperative mechanisms in the lap position.

Referring to Fig. 1 particularly, 1 will describe the detail construction of the iniprovements forming the essential feature of this invention, as combined with the triple valve mechanism. The triple valve illustrated need not be described in detail, comprising as it does a conventional construction including the triple piston 1, its stem 2, the main or triple slide valve 3, emergency piston a, and emergency and check valves 5 and 6 respectively. The train pipe is connected with the casing of the valve mechanism at 7 so that train pipe pressure will be admitted to the chamber A which is connected by a passage 8 with the chamber B that contains a graduating spring 9 and other parts, from which chamber B the train pipe pressure passes into the triple piston chamber C through the small passages 10 in the end wall of said chamber. Auxiliary air pressure from the auxiliary reservoir is admitted to the chamber D as usual, the stem of the triple piston 1, and the slide valve 3, operating in the chamber D as customary. At the other end of the chamber B and separated from said chamber by a partition 11 is the auxiliary chamber E which contains the motor or working piston 12 located at one side of said partition 11. At its opposite side the partition 11 supports a small cylinder 13 which is preferably an extension of the partition and in said cylinder 13 operates a normalizing piston 14 which is of considerably smaller area than the piston 12. A stem 15 connects the two pistons 12 and 14 and a stem 16 projects from the piston 1-1 in the direction of the triple piston 1. The stem 16 is located in substantial alinement with a graduating stem 17 which projects from the triple piston 1 and has the annular shoulder 18 intermediate its ends. Surrounding the cylinder 13 and having a hearing at one end against the partition 11 is the coiled spring 9 previously referred to, the opposite end of said spring engaging in a suitable flange of a thimble 19 which is held against the wall 20 of the chamber C,

' through the center of said partition establishing communication between the chamber E and the interior of the cylinder 13. 1 Since the chamber 13 is constantly supplied with train pipe air pressure, in the event of leakage of the air from one side of the piston 14 into the space between said piston and the partition 11, owing to the fact that the valve portion 15 of the stem 15 is seated firmly in its seat provided on said partition, there is no likelihood of escape of the air from said space while the parts are arranged as illustrated in Fig. 1. WVhen, however, the piston 14 is caused to move. toward the triple piston 1 as hereinafter described, the tubular member 21 is opened and air in the space between the parts 11 and 14 will then be free to pass by the stem 15 into the chamber E and from thence out of the chamber E to the atmosphere through a vent 22. The chamber E is always connected with the atmosphere at one side of the piston 12 and at the opposite side of the said piston said chamber E is connected by a passage 23 with a casing 24 beneath the chamber C, in which casing is mounted a controlling slide valve 25. A passage 26 leads from the valve chamber of the casing 24 to the atmosphere and said passage 26 is adapted to be connected by the cavity 27 of the valve 25, withv the passage 23 as shown in Fig. 1. Train pipe air pressure is .maintained in the valve chamber of the casing 24 under all conditions by the provision of the passage 28 leading from the passage 8 into said valve chamber. Furthermore a second passage 29 connects the valve chamber of casing 24 with the chamber D containing the triple slide valve 2 so that under certain conditions the passages 29 and a pas sage 30 connecting the passage 8 with the interior of the casing 24, may be put into communication with one another by movement of the valve 25 (see Fig. 2). However, in the position of the valve 25 in Fig. 1 the lower end of the passage 29 is closed by the .valve 25, and the end of the passage 30 communicating with the casing 24 is likewise closed. The valve 25 has a stem 31 connecting it with a control piston 32 which is mounted in a small piston chamber 33 at one end of the casing 24. A passage 34 connects the piston chamber 33 with the triple slide valve chamber D and when the slide valve 3 is in its release position as in Fig. 1, auxiliary air pressure passes from the chamber D through the passage 34 and acts on the left side of the piston 32. A coiled spring 35 encircles the stem 36 of the piston 32 and is adjusted by a suitable nut 37 so as to exert against the left hand side of the piston 32 a pressure of approximately sixtyfive pounds, which is equal, therefore, to the train pipe pressure in the casing 24,'the latter being also sixty-five pounds normally.

It is apparent from the foregoing that owing to the fact that the piston 32 is acted on upon its left side by the auxiliary air pressure admitted through passage 34 into chamber 33, and also by the pressure of the spring 35, the piston 32 and the connected valve Will be maintained at the right hand limit of its movement when the triple valve is in release position as shown in Fig.

1. In other words, the pressure against the plston 32 when the triple valve is at release is much greater than the train pipe pressure,

in the chamber O and in the casing 24 connected therewith.

Before describing the operation of the parts as above set forth it may be noted that the point of connection of the passage 34 with the chamber D is proximate to the inner end of an airexhaust passage 38 which leads from the chamber D to the atmosphere and which passage, by movement of the slide valve 3 to lap and service positions, will be connected by a cavity 39 inthe bottom of the valve 3 with the passage 34, thereby ermitting the auxiliary air pressure in the chamber 33 to exhaust to the atmosphere. I

Referring now to Fig. 2 which illustrates the triple valve mechanism in lap position, it will be assumed that owing to wearing of the packing of the triple piston 1, or some analogous cause, the piston 1 fails to respond to the action of the increased pres sure in the train pipe which ordinarily is sufficient to force said piston 1 to its release position in Fig. 1. 'VVhen the valve 3 assumed its service position in Fig. 2 it connected the passages 38 and 34 and thereby exhausted the auxiliary air pressure from the chamber 33 leaving the pressure of the spring 35 alone to maintain the piston 32 in its positionin Fig. 1. However, on the rise in the train pipe pressure to release the has been caused by the piston 32 responding promptly to the rise in train pipe pressure carries the valve 25 sufficiently to the left to disconnect the passages 23 and 26 and cause communication of the passage 23 with the interior of the casing 24 which contains the train pipe air pressure. Immediately this is done the train pipe air pressure passes along the passage 23 from the casing 24, enters the chamber E at the left hand side of the motor piston 12 and forces the piston 12 to the right into a position such as shown in Fig. 2. In this operation the train pipe air pressure is caused to move the motor piston 12 notwithstanding that said pressure is acting on the small piston 14: to resist such movement, the movement being effected owing to the different areas of the pistons 12 and 14. In their movement to the right the pistons 12 and 14 cause the stem 16 to impinge against the graduating stem 17 of the triple piston 1 and by this engagement the triple piston 1 is forcibly moved in the same direction as the said movement of the pistons 12 and 14, or in other words, said. triple piston l is carried to the release position illustrated in Fig. 1, simultaneously moving the main valve 3 to its release position from the lap position in Fig. 2. As soon as the parts 1 and 3 have been carried from their positions as shown in Fig. 2 to the positions thereof as shown in Fig. 1 the valve 3 reestablishes communication between the passage 3 1 and the chamber D so that the auxiliary air pressure from the chamber D again enters the chamber 33 at the left hand side of the piston as disposed in Fig. 2 and supplements the pressure or tension of the spring 35, thereby overcoming the train pipe pressure at the right hand side of the piston 32 and forcing said piston 32 and the valve 25 to the normal position of said parts as illustrated in Fig. 1.

The only thing remaining to be done to restore the control mechanism of this invention to its normal condition is to normalize the parts 12 and 1 1. This normalizing is accomplished owing to the fact that the restoration of the valve 25 to its position in Fig. 1 again connects the passages 23 and 26 so that the train pipe pressure which was previously admitted to the left hand end of the chamber E is now permitted to exhaust from said chamber to the atmosphere through the passages 23 and 26. Thereupon the train pipe pressure in the cylinder 13 acting on the small piston 14: moves said piston from the position shown in Fig. 2 to its normal position as shown in Fig. 1, said pressure being, of course, more than suflicient to overcome the friction intermediate the pistons 12 and 14 and the walls of their respective piston chambers.

with the use of the control mechanism hereinbefore described the prompt releasing of the air brakes is effected by piston means operated by the train pipe pressure and acting on the triple piston only when the abnormal condition of failure of said piston to move to release position occurs.

In addition to the function of the control mechanism as already set forth, I have designed said mechanism to perform still another function, namely that of controlling the operation of the triple valve in the event of an overcharge of air pressure. lVhen the overcharge occurs the greater pressure in the auxiliary reservoir which is connected with the chamber D forces the triple piston 1 to lap position which connects the cavity 39 of the slide valve 3 with the passages 38 and 34, promptly exhaust ing the auxiliary air pressure from the chamber 33. As soon as this happens the increased train pipe pressure in the valve casing 2A1, being above sixty-five pounds, forces the piston 32 and the valve 25 leftward, whereupon the passages 30 and 29 are connected by means of the cavity 27 of the slide valve 25. This permits the over charge to pass from the auxiliary reservoir to the chamber A and at the same time the passage 23 is placed in communication with the casing 21 and train pipe pressure passes from said casing 2st to the chamber E and acts on the piston 12 in the same manner as hereinbefore described.

hen a service application of the brakes is made it will be understood that the reduction of pressure must not be less than five pounds or the brakes will not apply, since it takes from three to five pounds reduction to move the triple piston to service. That is to say, if the triple piston moves to service with a three or four pound reduction it leaves one or two pounds of pressure in the brake pipes in excess of the adjustment of the spring 35, the reduction still being made in the brake pipe, but if the brake pipe reduction should be very slow, consuming about two or three seconds time reducing to sixty-five pounds the fact that the cavity 39 is made small permits a small quantity of pressure to remain in chamber 33 for approximately ten seconds of time, thereby assisting spring 35 to hold piston 32 to the right or closed position until brake pipe pressure reduces to sixty-five pounds. Obviously brake pipe pressure can be reduced as quickly as desired and it will be apparent that brake pipe pressure and pressure in chamber 33 need not exhaust at the same time as the valve 25 and piston 32 will not operate until the brake pipe pressure rises up to the adjustment of spring 35, thus giving chamber 33 time to exhaust to atmospheric pressure before it will have to operate again. In other words, cavity 39 being small allows brake pipe pressure to re duce to sixty-five pounds before chamber 33 exhausts all of its pressure but brake pipe pressure can be reduced. to sixty-five pounds as quickly as desired asthe chamber 33 does not afiect this reduction. Moreover, pres sure in chamber 33 may exhaust for any length of time after the triple goes to service because said chamber only has to be at atmospheric pressure when charging so that if the triple fails to release due to worn packing rings, brake pipe pressure when raised to sixty-five pounds will force piston 32 into open position, as has been explained.

On passenger trains the spring 35 will be set to exert a pressure equivalent to that carried in the brake pipe because there is'little or no brake pipe friction in short trains, but in long freight trains when brake pipe friction makes the pressure seventy pounds on the head end of the train and sixty-seven and sixty-eight pounds at the rear end of the train, the spring will be set at sixty-five pounds so that in charging brake pipe pres sure will operate the forcible release. Cavity 39 is connected to the atmosphere in all positions but release so it is apparent that pressure can pass out'of chamber 33 even after the. brake pipe pressure has been reduced and triple returned to lap. Cavity 39 may be made extremely small as it will have a period of time extending from the movement of the triple to service until release of the brakes and recharge has taken place before it is necessary to be exhausted to atmospheric pressure.

When my invention is used on certain known equipment the passage 29 that connects with the auxiliary reservoir pressure is provided with a branch communicating with the supplementary reservoir. Said branch leads from the passage 29 and when the triple valve goes to lap position the supplementary reservoir is cut out. In other words, the passage 29 is connected with both the auxiliary and supplementary reservoirs so as to let off the overcharge of each reservoir under practical conditions of service.

Having thus described my invention, what I claim as new is q 1. In a fluid presure brake system, the combination with triple valve means including a main valve, and a triple piston as sociated with said main valve and adapted to be moved to service position by reduction of train. pipe pressure, of mechanical means capable of engaging said triple piston and forcing the same to release position, and

automatic means for causing operation of the last mentioned means.

2. In a fluid pressure brake system, the combination-with a triple valve mechanism including a triple piston and main valve connected therewith, of train pipe pressure connections for supplying air to act on the triple piston so that on increase of train pipe pressure the latter will move to release position, and automatic means for restoring said triple piston to release position in the event said piston does not respond to :the action of the train pipe pressure. I i

3. In combination, triple valve mechanism including a main valve and triple piston associated therewith, auxiliary means to move the triple piston to release position, and automatic controlling means for said auxiliary means.

4:. In combination, triple valve mechanism including a main valve and triple piston associated therewith, auxiliary means to move the triple piston to release position, and means governing the operation of said auxiliary means and controlled in its action b the main valve aforesaid.

5. In combination, triple valve mechanism comprising a main valve and its associated triple piston, a triple piston chamber, means for supplying train pipe air pressure to said chamber, a valve chamber'receiving said valve, means for supplying auxiliary reservoir pressure'to the said valve chamber, said train pipe and auxiliary pressures acting on opposite sides of the triple piston, a motor arranged to forcibly move the triple piston to release position in the event the same does not respond to the action of the train pipe pressure, and automatic controlling means for said motor. I

6. In combination, triple valve mechanism comprising a main valve and its associated triple piston, a triple piston chamber, means for supplying train pipe air pressure to said chamber, a valve chamber receiving said valve, means for supplying auxiliary reservoir pressure to the said valve chamber, said train pipe and auxiliary pressures acting on opposite sides of the triple piston, a motor arranged to forcibly move the triple piston to release position in the event the same does not respond to the action of the train pipe pressure, and automatic controlling means for said motor governed in its operation by the position of the main valve.

7. In combination, triple valve mechanism comprising a main'valve and its associated triple'piston, a triple piston chamber, means for supplying train pipe air pressure to said chamber, a valve chamber a receiving said valve, means for supplying auxiliary reser voir pressure to the said valve chamber, said train pipe and auxiliary pressures acting on opposite sides of the triple piston, amotor arranged to forcibly move the triple piston to release position in the event the same does not respond tothe action of the train pipe pressure, and automatic controlling means for said motor comprising a control piston acted on by the train pipe and auxiliary reservoir pressures at opposite sides thereof, means supplementing the action of the auxiliary reservoir pressure in respect to said control piston, and control valve means operable by said control piston whereby to cause said motor to be operated by the train pipe pressure.

8. In an automatic fluid pressure brake system, a triple valve device comprising a mam valve, a triple piston for operating said main valve, a normally inactive motor for moving said triple piston to release position when the same fails to respond to train pipe pressure acting thereon, and control mechanism for said motor automatically operable by the train pipe pressure and gov erned in its operation by said main valve.

9. In a fluid pressure brake system, a triple valve device comprising a main valve, a triple piston connected with the main valve, a working piston, means intermediate the working piston and the triple piston whereby to forcibly move the latter to release position, and automatically operating controlling mechanism for said working piston.

10. In a fluid pressure brake system, a triple valve device comprising a main valve, a triple piston connected with the main valve, a working piston, means intermediate the working piston and the triple piston whereby to forcibly move the latter to release position, and automatically operating controlling mechanism for said working piston governed by positioning of the main valve through the action of the triple piston.

11. In a fluid pressure brake system, a triple valve device comprising a main valve, a triple piston connected with the main valve, a working piston, means intermediate the working piston and the triple piston whereby to forcibly move the latter to release position, automatically operating controlling mechanism for said working piston, said controlling mechanism comprising a control piston and means for supplying train pipe pressure and auxiliary reservoir pressure to act upon said piston at opposite sides, and valve mechanism operable by said control piston to cause train pipe pressure to act on the working piston under predetermined conditions of service.

12. In combination, a triple valve device comprising a main valve and triple piston associated therewith, train pipe pressure supply means adapted to supply train pipe air to act on the triple piston at one side of the same, auxiliary reservoir pressure supply means adapted to supply auxiliarv reservoir air to act on the triple piston at the opposite side thereof, and controlling means governing the action of said parts and including a control piston, means for supplying train pipe pressure to act on said control piston at one side of the same, and means for supplying auxiliary reservoir pressure to act on said control piston at the opposite side of the same, and valve means operable by said control piston to connect the auxiliary reservoir pressure supply means with the train pipe pressure supply means, the main valve having means to exhaust the auxiliary reservoir air pressure acting on the control piston.

13. In combination, a triple valve device comprising a main valve and triple piston associated therewith, train pipe pressure supply means adapted to supply train pipe air to act on the triple piston at one side of the same, auxiliary reservoir pressure supply means adapted to supply auxiliary reservoir air to act on the triple piston at the opposite side thereof, and controlling means governing the action of said parts and including a control piston, means for supplying train pipe pressure to act on said control piston at one side of the same, and means for supplying auxiliary reservoir pressure to act on said control piston at the opposite side of the same, and valve means operable by said control piston to' connect the auxiliary reservoir pressure supply means with the train pipe pressure supply means, the main valve having means to exhaust the auxiliary reservoir air pressure acting on the control piston when the triple piston assumes its service position.

14. In combination, a triple valve device comprising a main valve and triple piston associated therewith, train pipe pressure supply means adapted to supply train pipe air to act onthe triple piston at one side of the same, auxiliary reservoir pressure supply means adapted to supply auxiliary reservoir air to act on the triple piston at the opposite side thereof, and controlling means governing the action of said parts and including a control piston, means for supplying train pipe pressure to act on said control piston at one side of the same, and means for supplying auxiliary reservoir pressure to act on said control piston at the opposite side of the same, valve'means operable by said control piston to connect the auxiliary reservoir pressure supply means with the train pipepressure supply means, the main valve having means to exhaust the auxiliary reservoir air pressure acting on the control piston when the triple piston assumes its service position, a motor capable of acting on the triple piston to force the same to release position, and means to supply air under pressure to saidmotor for actuating the same when the control piston assumes a predetermined position.

15. In combination, a triple valve device comprising a main valve and triple piston associated therewith, train pipe pressure supply means adapted to supply train pipe air to act on the triple piston at one side of the same, auxiliary reservoir pressure sup gas ply means adapted to supply auxiliary reservoir air to act on the triple piston at the opposite side thereof, and controlling means governing the action of said parts and. including a control piston, means for supplying train pipe pressure to act on said control piston at one side of the same, and means for supplying auxiliary reservoir pressure to act on said control piston at the vopposite side of the same, valve means operable by said control piston to connect the auxiliary reservoir pressure supply means with the train pipe pressure supply means, the main valve having means to exhaust the auxiliary reservoir air pressure acting on the control piston when the triple piston assumes its service position, a motor capable of acting on thetriple piston to force the,

same to release position, and means to supply air under pressure to said motor for actuating the same when the control piston assumes a predetermined position, and means acting on the control piston to supplement the action of the auxiliary reservoir pressure supply means.

16. In combination, a triple valve device comprising a main valve, a triple piston connected therewith, train pipe pressure supply means for supplying pressure to act on the triple piston at one side ofthe same, auxiliary reservoir pressure supply means for supplying pressure to act on the triple piston at the opposite side thereof, a motor piston, means intermediate the motor piston and the triple piston whereby the former may forcibly move the latter to release position, automatic controlling means for the motor piston, and means for normalizing the motor piston after the same has caused the triple piston to assume release position.

.17. In combination, a triple valve device comprising a main valve, a triple piston connected therewith, means for supplying train pipe pressure to act on the triple piston at one side of the same, auxiliary reservoir pressure supply means for supplying pressure to act on the triple piston at the opposite side thereof, a motor piston, means intermediate the motor piston and the triple piston whereby the former may forcibly move the latter to release position, automatic controlling means for the motor piston, and

means for normalizing the motor piston after the same has caused the triple piston to assumerelease position, and operable by the train pipe pressure supplied from the train pipe pressure supply means. v

18., In combination, a triple valve device comprising a main valve, a triple piston connected therewith, means for supplying train pipe pressure to act on the triple piston at one side of the same, auxiliary reservoir pressure supply means for supplying pressure to act on the triple piston at the opposite side thereof, a motor piston, means inmeans for normalizing the motor piston after the same has caused the triple piston to I assume release position, and comprising a piston of smaller area than the motor piston and operable by the train pipe pressure directly acting thereon.

19. In combination, a triple valve device V comprising a main valve, a triple piston connected therewith, means for supplying train pipe pressure to act on the triple piston at one side of the same, auxiliary reservoir pressure supply means for supplying pressure to act on the triple piston at the opposite side thereof, a motor-piston, meansintermediate the motor piston and the triple piston whereby the former may forcibly move the latter to release position, automatic controlling means for the motor piston, means for normalizing the motor piston after the same has caused the triple piston to assume release position and comprising a piston of smaller area than the motor piston and operable by the train pipe pressure directly acting thereon, and a stem connecting the normalizing piston andvthe motor piston and forming a valve controlling escape of the train pipe pressure air from the motor mechanlsm.

20. In an automatic fluid pressure brake system, triple valve means including a triple piston, means for supplying train pipe and auxiliary reservoir air to act on said piston, means for forcibly moving the triple piston to release position when the same fails to respond to normal action of the mechanism whereby it is usually moved to said position, and control means governing the action of the last mentioned means and controlled by auxiliary reservoir pressure from the auxiliary reservoir air supply means. 7

21. In an automatic fiuid'pressure brake system, triple valve means including a triple piston, means for supplying train-pipe and auxiliary reservoir air to act on said piston, means for forcibly moving the triple piston to release position when the same fails to respond to normal action of the mechanism whereby it is usually moved to said position,

position when the same fails to assume such position under normal action of the mechanism comprising a working piston, means for supplying train pipe air pressure to act on said working piston, and control means for said air supply means preventing the supply of air to act on the working piston except under abnormal conditions of operation of the triple piston.

23. In an automatic fluid pressure brake system, the combination of triple valve mechanism including a triple piston, means for causing said piston to move to release position when the same fails to assume such position under normal action of the mechanism comprising a working piston, means for supplying train pipe air pressure to act on said working piston, control means for said air supply means preventing the supply of air to act on the working piston except under abnormal conditions of operation of the triple piston, and means associated with the working piston operable by the train pipe air pressure to normalize said working piston.

24. In an automatic fluid pressure brake system, the combination of triple valve mechanism including a triple piston, a piston chamber, a working piston mounted in said chamber, a normalizing piston con nected with said working piston and of smaller area than said working piston, a separate piston chamber containing the normalizing piston, train pipe pressure supply means normally acting on said normalizing piston, control means whereby to supply said train pipe pressure to act on the work ing piston, and means operable by said working piston to move the triple piston to release position.

9-5. In an automatic fluid pressure brake system, the combination of triple valve mechanism including a triple piston, a piston chamber, a working piston mounted in said chamber, a normalizing piston connected with said working piston and of smaller area than said working piston, a separate piston chamber containing the normalizing piston, train pipe pressure supply means normally acting on said normalizlng piston, control means whereby to supply said train pipe pressure to act on the working piston, and means operable by said Working piston to move the triple piston to release position, said control means including a control piston, means for supplying auxiliary reservoir pressure to act on said control piston, a valve operable by said control piston to govern the supplying of train pipe pressure to act on the working piston, a spring cooperating with the control piston to supplement the action of the auxiliary reservoir pressure thereon to hold said valve in a position preventing the train pipe pressure from acting on the working piston, and a passage to supply train pipe pressure to act on said control piston and thereby move its associated valve into a position for supplying train pipe pressure to act on the working piston.

In testimony whereof, I atlix my signature in presence of two witnesses.

WVALTER F. ATWOOD. WVitnesses:

W. H. MADDY, BYRON F. WYNN.

Copies of this patent may be obtained for five cents each, by addressing the "Commissioner of Patents, Washington, I). 0. 

